This invention relates to improvements in electric switches, and it relates particularly to improvements in push-button switches.
While not limited thereto, the invention is particularly applicable to push-button switches of a kind in which a plunger is mounted for reciprocation within the switch housing. Part of the plunger extends from the housing and is urged to that extended position by an internal bias spring. Upon depressing the plunger, the switch is actuated, and when it is released, the bias spring returns the actuator to initial extended position, without reactuating the switch.
Both the plunger, at a point inside the housing, and the housing itself, are formed with cam surfaces that cooperate with cam follower surfaces that are formed on a ratchet. The ratchet is moveable relative to the plunger and to the housing, and it is moved in one direction by depression of the plunger. In a common form, the bias spring acts both on the ratchet and on the plunger to return them after depression of the plunger. The cam surfaces are arranged so that the ratchet is made to rotate, or index, through an angle of rotation perpendicular to the axis of the plunger and ratchet reciprocation.
The cam surfaces are arranged so that the ratchet comes to rest at one of two positions in the direction of its axial movement. Those two positions are assumed alternately as the switch plunger is pressed successively. The ratchet is made to bear upon a moveable contact of the switch, and in one ratchet position the moveable contact is held away from the fixed contacts of the switch, and in the other axial position of the ratchet the moveable contact is permitted to engage the fixed contacts of the switch.
That kind of a mechanism lends itself to inclusion in the cylindrical mounting stem of what the industry calls a "one-hole mounting switch." Units of that kind have gained wide acceptance as power control switches for a wide variety of small electrical appliances. That wide acceptance can be accounted for by the fact that such switches can be produced at low cost and because the push-button indexing mechanism can easily be made long-lived and reliable. However, the reliability of the electrical operation of such switches has not matched the reliability of the push-button ratcheting structure. Heretofore, attempts to improve electrical reliability have been accomplished only at increased manufacturing costs.